Fix comment confusion bug in update_lib (#7802)

* Use `unittest.expectedSuccess` to mark failing tests

* Fix comment find logic

* Add test for it

scripts/update_lib/patch_spec.py

@@ -190,13 +190,23 @@ class PatchEntry(typing.NamedTuple):
                     if ut_method.has_cond():
                         cond = ast.unparse(dec_node.args[0])
                 else:
-                    # Search first on decorator line, then in the line before
-                    for line in lines[dec_node.lineno - 1 : dec_node.lineno - 3 : -1]:
-                        if found := re.search(rf"{COMMENT}.?(.*)", line):
-                            reason = found.group()
-                            break
+                    pattern = re.compile(rf"{COMMENT}.?(.*)")
+                    dec_lineno = dec_node.lineno
+
+                    curr_line = lines[dec_lineno - 1]
+                    prev_line = lines[dec_lineno - 2]
+
+                    # If we see our comment at the decorator line, take it
+                    if found := pattern.search(curr_line):
+                        reason = found.group()
+                    elif prev_line.strip().startswith("#") and (
+                        found := pattern.search(prev_line)
+                    ):
+                        # Search the previous line of the decorator,
+                        # only take the comment if the line starts with a `#`
+                        reason = found.group()
                     else:
-                        # Didn't find our `COMMENT` :)
+                        # Didn't find our `COMMENT`, so the patch isn't ours :)
                         continue
 
                 reason = reason.removeprefix(COMMENT).strip(";:, ")

scripts/update_lib/tests/test_patch_spec.py

@@ -149,6 +149,30 @@ class TestFoo(unittest.TestCase):
         specs = patches["TestFoo"]["test_one"]
         self.assertEqual(len(specs), 2)
 
+    def test_comment_confusion(self):
+        """
+        Test that we only extract our patches when CPython set one of the UT methods,
+        that we search for
+        """
+
+        code = f"""
+class TestFoo(unittest.TestCase):
+    @unittest.expectedSuccess # {COMMENT}; reason
+    @unittest.expectedFailure
+    def test_one(self):
+        pass
+        """
+
+        patches = extract_patches(code)
+        specs = patches["TestFoo"]["test_one"]
+        self.assertEqual(len(specs), 1)
+
+        spec = specs[0]
+        self.assertEqual(
+            spec,
+            PatchSpec(ut_method=UtMethod.ExpectedSuccess, cond=None, reason="reason"),
+        )
+
 
 class TestApplyPatches(unittest.TestCase):
     """Tests for apply_patches function."""